The compact-open topology #
In this file, we define the compact-open topology on the set of continuous maps between two topological spaces.
Main definitions #
ContinuousMap.compactOpen
is the compact-open topology onC(X, Y)
. It is declared as an instance.ContinuousMap.coev
is the coevaluation mapY → C(X, Y × X)
. It is always continuous.ContinuousMap.curry
is the currying mapC(X × Y, Z) → C(X, C(Y, Z))
. This map always exists and it is continuous as long asX × Y
is locally compact.ContinuousMap.uncurry
is the uncurrying mapC(X, C(Y, Z)) → C(X × Y, Z)
. For this map to exist, we needY
to be locally compact. IfX
is also locally compact, then this map is continuous.Homeomorph.curry
combines the currying and uncurrying operations into a homeomorphismC(X × Y, Z) ≃ₜ C(X, C(Y, Z))
. This homeomorphism exists ifX
andY
are locally compact.
Tags #
compact-open, curry, function space
The compact-open topology on the space of continuous maps C(X, Y)
.
Equations
- One or more equations did not get rendered due to their size.
Definition of ContinuousMap.compactOpen
.
C(X, ·)
is a functor.
Alias of ContinuousMap.continuous_postcomp
.
C(X, ·)
is a functor.
If g : C(Y, Z)
is a topology inducing map,
then the composition ContinuousMap.comp g : C(X, Y) → C(X, Z)
is a topology inducing map too.
Alias of ContinuousMap.isInducing_postcomp
.
If g : C(Y, Z)
is a topology inducing map,
then the composition ContinuousMap.comp g : C(X, Y) → C(X, Z)
is a topology inducing map too.
Alias of ContinuousMap.isInducing_postcomp
.
If g : C(Y, Z)
is a topology inducing map,
then the composition ContinuousMap.comp g : C(X, Y) → C(X, Z)
is a topology inducing map too.
If g : C(Y, Z)
is a topological embedding,
then the composition ContinuousMap.comp g : C(X, Y) → C(X, Z)
is an embedding too.
Alias of ContinuousMap.isEmbedding_postcomp
.
If g : C(Y, Z)
is a topological embedding,
then the composition ContinuousMap.comp g : C(X, Y) → C(X, Z)
is an embedding too.
Alias of ContinuousMap.isEmbedding_postcomp
.
If g : C(Y, Z)
is a topological embedding,
then the composition ContinuousMap.comp g : C(X, Y) → C(X, Z)
is an embedding too.
C(·, Z)
is a functor.
Alias of ContinuousMap.continuous_precomp
.
C(·, Z)
is a functor.
Precomposition by a continuous map is itself a continuous map between spaces of continuous maps.
Equations
- ContinuousMap.compRightContinuousMap Z f = { toFun := fun (g : C(Y, Z)) => g.comp f, continuous_toFun := ⋯ }
Instances For
Any pair of homeomorphisms X ≃ₜ Z
and Y ≃ₜ T
gives rise to a homeomorphism
C(X, Y) ≃ₜ C(Z, T)
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Precomposition by a homeomorphism is itself a homeomorphism between spaces of continuous maps.
Equations
- ContinuousMap.compRightHomeomorph Z f = f.symm.arrowCongr (Homeomorph.refl Z)
Instances For
Composition is a continuous map from C(X, Y) × C(Y, Z)
to C(X, Z)
,
provided that Y
is locally compact.
This is Prop. 9 of Chap. X, §3, №. 4 of Bourbaki's Topologie Générale.
The evaluation map C(X, Y) × X → Y
is continuous
if X, Y
is a locally compact pair of spaces.
Equations
- ⋯ = ⋯
Alias of ContinuousEval.continuous_eval
.
Evaluation of a bundled morphism at a point is continuous in both variables.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
For any subset s
of X
, the restriction of continuous functions to s
is continuous
as a function from C(X, Y)
to C(s, Y)
with their respective compact-open topologies.
The compact-open topology on C(X, Y)
is equal to the infimum of the compact-open topologies on C(s, Y)
for s
a compact subset of X
.
The key point of the proof is that for every compact set K
,
the universal set Set.univ : Set K
is a compact set as well.
Alias of ContinuousMap.compactOpen_eq_iInf_induced
.
The compact-open topology on C(X, Y)
is equal to the infimum of the compact-open topologies on C(s, Y)
for s
a compact subset of X
.
The key point of the proof is that for every compact set K
,
the universal set Set.univ : Set K
is a compact set as well.
Alias of ContinuousMap.nhds_compactOpen_eq_iInf_nhds_induced
.
A family F
of functions in C(X, Y)
converges in the compact-open topology, if and only if
it converges in the compact-open topology on each compact subset of X
.
The coevaluation map Y → C(X, Y × X)
sending a point x : Y
to the continuous function
on X
sending y
to (x, y)
.
Equations
- ContinuousMap.coev X Y b = { toFun := Prod.mk b, continuous_toFun := ⋯ }
Instances For
The coevaluation map Y → C(X, Y × X)
is continuous (always).
The curried form of a continuous map α × β → γ
as a continuous map α → C(β, γ)
.
If a × β
is locally compact, this is continuous. If α
and β
are both locally
compact, then this is a homeomorphism, see Homeomorph.curry
.
Equations
- f.curry = { toFun := fun (a : X) => { toFun := Function.curry (⇑f) a, continuous_toFun := ⋯ }, continuous_toFun := ⋯ }
Instances For
Auxiliary definition, see ContinuousMap.curry
and Homeomorph.curry
.
Equations
- f.curry' a = f.curry a
Instances For
If a map α × β → γ
is continuous, then its curried form α → C(β, γ)
is continuous.
To show continuity of a map α → C(β, γ)
, it suffices to show that its uncurried form
α × β → γ
is continuous.
The currying process is a continuous map between function spaces.
The uncurried form of a continuous map X → C(Y, Z)
is a continuous map X × Y → Z
.
The uncurried form of a continuous map X → C(Y, Z)
as a continuous map X × Y → Z
(if Y
is
locally compact). If X
is also locally compact, then this is a homeomorphism between the two
function spaces, see Homeomorph.curry
.
Equations
- f.uncurry = { toFun := Function.uncurry fun (x : X) (y : Y) => (f x) y, continuous_toFun := ⋯ }
Instances For
The uncurrying process is a continuous map between function spaces.
The family of constant maps: Y → C(X, Y)
as a continuous map.
Equations
- ContinuousMap.const' = ContinuousMap.fst.curry
Instances For
Currying as a homeomorphism between the function spaces C(X × Y, Z)
and C(X, C(Y, Z))
.
Equations
- Homeomorph.curry = { toFun := ContinuousMap.curry, invFun := ContinuousMap.uncurry, left_inv := ⋯, right_inv := ⋯, continuous_toFun := ⋯, continuous_invFun := ⋯ }
Instances For
If X
has a single element, then Y
is homeomorphic to C(X, Y)
.
Equations
- Homeomorph.continuousMapOfUnique = { toFun := ContinuousMap.const X, invFun := fun (f : C(X, Y)) => f default, left_inv := ⋯, right_inv := ⋯, continuous_toFun := ⋯, continuous_invFun := ⋯ }